The admission from the White House about the early timing of a discussion about war strategy came after the administration was questioned about a new book by journalist Bob Woodward.
The revelation is sure to fire up some of Bush's critics who have accused him of being too eager to go to war against Iraq and of diverting resources from the hunt for Usama bin Ladin, the mastermind of the September 11 attacks.
The book, entitled Plan of Attack, is not due to be released until next week, but the Associated Press published some details from it after obtaining an early copy.
Weapons of mass destruction
According to the Associated Press, the book reveals that Bush took Defence Secretary Donald Rumsfeld aside on 21 November 2001, and asked him to come up with a fresh war plan.
That request came less than two months after the United States launched a war on Afghanistan and a year and a half before the March 2003 invasion of Iraq.
Donald Rumsfeld was asked to
draw up the war plans
Bush cited Saddam's alleged weapons of mass destruction as the main reason for the invasion, in which almost 700 US troops have died as well as thousands of Iraqi military and civilians. No such weapons, however, have been found.
Two former officials from his administration, ex-Treasury Secretary Paul O'Neill and former counterterrorism chief Richard Clarke, have portrayed the president as fixated on Iraq, even at a time when the administration has insisted Bush was focused squarely on Afghanistan.
Bush's memory 'foggy'
At a news conference with British Prime Minister Tony Blair on Friday, the president was asked if the Woodward account about the conversation with Rumsfeld in November 2001 was correct.
Bush said his memory was foggy.
"You know, I can't remember exact dates that far back"
"You know, I can't remember exact dates that far back," he said.
Later, at a news briefing, White House spokesman Scott McClellan confirmed the November conversation, saying the topic of an Iraq war plan was only raised when it became clear the United States was winning the war in Afghanistan.
"We began combat operations in Afghanistan in the earlier period of October, and by November and early December things were winding down," McClellan said.
"And the President did talk to Secretary Rumsfeld about Iraq," he added.
Concern for Blair
A separate account of the Woodward book published in the Washington Post said that in December 2001 Bush met repeatedly with Army General Tommy Franks and his war cabinet to plan the attack on Iraq. The war planning became so intensive that it set in motion a chain of events that would have been difficult to reverse.
Thousands have died since the
US-led invasion of Iraq in 2003
Bush made up his mind to go to war in January 2003, but held off for two months out of concern for the political impact on British Prime Minister Tony Blair, the newspaper said. Blair's decision to join the United States in the war is highly unpopular in Britain.
Woodward, the reporter who broke the Watergate scandal that led to the resignation of President Richard Nixon in the 1970s, is an assistant managing editor at The Washington Post.